Year	Percent
1991	21.274
1992	20.498
1993	20.144
1994	19.596
1995	19.202
1996	18.863
1997	18.752
1998	18.682
1999	18.254
2000	21.864
2001	27.342
2002	27.397
2003	27.607
2004	27.477
2005	27.335
2006	27.428
2007	27.257
2008	27.27
2009	27.27
2010	26.645
2011	26.42
2012	27.659
2013	28.308
2014	29.157
2015	29.898
2016	30.25
2017	30.4
2018	30.852
2019	31.732
2020	32.006
2021	32.288
2022	32.553